(define (double x)
    (+ x x))
(define (halve x)
    (/ x 2))
(define (fast-multi a b)
    (cond ((= b 0) 0)
        ((even? b) (double (fast-multi a (halve b))))
        (else (+ 3 (fast-multi a (- b 1))))
    )
)        
(display (fast-multi 3 5))
(exit)
